[selowitch]

Got my iMac 20" spanning its display with a 19" Dell flatscreen. Looks great. There are issues of a mismatch, however. The Dell's max resolution is 1280 x 1024, while the iMac's is 1680 x 1050. I also think the Dell's pixels might be bigger. I don't like it when I drag window from the lower part of the Dell screen and when it reaches the iMac's screen, the window assumes a smaller shape (so it doesn't look continguous or continous).

Any advice?

[Tenex]

You can't expect a single app window to span the two displays and be contiguous as they are different vertical resolutions. I span to a 17" 1280x1024. It only makes sense to display an app on one or other screen.

you could lower the res on the iMac but it would look horrible IMO.